Physicochemical and sensory properties of tofu prepared with heat-treated soybeans

The sensory characteristics of tofu made from soybeans (var. TaeKwang) heat treated at 60C for 60, 120 and 180 min were investigated to determine the effects of heat shock on the texture and flavor of tofu, which play an important role in consumer preference. Hardness and chewiness increased with heat treatment, reaching maxima at 120 min, while cohesiveness decreased significantly with heat treatment in the 120 min sample. Sensory evaluation showed that the smoothness and homogeneity of the surface of the tofu increased with heat treatment from those of the control. Grassy aroma, which is one of the main undesirable flavors of tofu, was decreased by the heat treatment. Firmness and elasticity both had a maximum value of 8.4 by the 15-cm line-scale evaluation in the 120 min treated samples, showing the practical possibility of using mild heat treatment to produce firm and elastic tofu. Increases in the 7S globulin due to heat treatment are thought to be responsible for the textural changes observed. PRACTICAL APPLICATIONS Texture and flavor are major factors in determining the quality of tofu. Tofu has become popular as a healthy food and its consumption is increasing, hence the necessity of producing tofu with various kinds of texture. We found that heat treatment on soybean used in tofu preparation can be one of the methods to control the texture of tofu. The grassy flavor of soy products is the limiting factor that seriously affects their consumption. According to our sensory evaluation, the grassy aroma was decreased significantly by heat treatment, showing that controlled heat treatment has a positive effect on the overall quality of tofu. This study suggests that heat treatment of soybeans can be applied to produce tofu with less grassy flavor and firmer texture.